Coexistence of intrinsic piezoelectricity and ferromagnetism induced by small biaxial strain in septuple-atomic-layer $\mathrm{VSi_2P_4}$

TL;DR

This study predicts that biaxial strain can induce coexistence of ferromagnetism and piezoelectricity in VSi2P4 monolayers, with potential applications in spin electronics, by tuning electronic phases and enhancing piezoelectric coefficients.

Contribution

It demonstrates strain-induced coexistence of ferromagnetism and piezoelectricity in VSi2P4 and VSi2N4 monolayers, revealing new multifunctional properties for spintronic applications.

Findings

Coexistence of ferromagnetism and piezoelectricity achieved in VSi2P4 under 0-4% strain.

Piezoelectric coefficients comparable to bulk materials (up to 5.27 pm/V).

Strain tunes electronic phases from ferromagnetic metal to half-metal.

Abstract

The septuple-atomic-layer $\mathrm{VSi_2P_4}$ with the same structure of experimentally synthesized $\mathrm{MoSi_2N_4}$ is predicted to be a spin-gapless semiconductor (SGS). In this work, the biaxial strain is applied to tune electronic properties of $\mathrm{VSi_2P_4}$, and it spans a wide range of properties upon the increasing strain from ferromagnetic metal (FMM) to SGS to ferromagnetic semiconductor (FMS) to SGS to ferromagnetic half-metal (FMHM). Due to broken inversion symmetry, the coexistence of ferromagnetism and piezoelectricity can be achieved in FMS $\mathrm{VSi_2P_4}$ with strain range of 0\% to 4\%. The calculated piezoelectric strain coefficients $d_{11}$ for 1\%, 2\% and 3\% strains are 4.61 pm/V, 4.94 pm/V and 5.27 pm/V, respectively, which are greater than or close to a typical value of 5 pm/V for bulk piezoelectric materials. Finally, similar to $\mathrm{VSi_2P_4}$, the coexistence of piezoelectricity and ferromagnetism can be realized by strain in the $\mathrm{VSi_2N_4}$ monolayer. Our works show that $\mathrm{VSi_2P_4}$ in FMS phase with intrinsic piezoelectric properties can have potential applications in spin electronic devices.